Immunoglobulin E antibody formation in response to homologous rabbit albumin heavily substituted with dinitrophenol: effect of adjuvant.

Although much progess has been made in the detection and characterization of homocytotropic antibodies, identification of the factors which control their synthesis remains to be determined. To assess the influence of different adjuvants on anti-dinitrophenol (DNP) immunoglobulin E (IgE) antibody responses, rabbits were immunized with adjuvant plus homologous albumin (HRA) heavily substituted with DNP (DNP30-HRA). This antigen in rabbits has a B cell-reactive determinant (DNP) and weak non-B cell-reactive determinants (new antigenic determinants) which sensitize rabbits for delayed-type hypersensitivity reactions to DNP30-HRA. It was postulated that the anti-DNP IgE response to DNP30-HRA could be regulated if the immunogenicity of the weak non-B cell-reactive determinants (new antigenic determinants) in DNP30-HRA could be manipulated by adjuvants and dosage. Complete Freund adjuvant and incomplete Freund adjuvant increased the immunogenicity of the new antigenic determinants in DNP30-HRA (10 mg) much more than did alum. However, equivalent primary anti-DNP IgE responses were made by all rabbits sensitized with this dose, regardless of the adjuvant used. Larger doses of DNP30-HRA (25 mg) in alum sensitized rabbits for strong delayed-type hypersensitivity reactions to DNP30-HRA and also elicited enhanced and persistent primary anti-DNP IgE responses. Enhanced but transient primary anti-DNP IgE responses were elicited by 25 mg of DNP30-HRA in incomplete Freund adjuvant. In contrast, no primary anti-DNP IgE responses were made to 25 mg of DNP30-HRA in complete Freund adjuvant. Regardless of the adjuvant or dosage used for primary immunization, no secondary anti-DNP IgE responses to DNP30-HRA were detected.